Catalytic body and method of making same.



TENT OFFICE.

KARL SCHICK, 0F GRIESHEIM-ON-THE-MAIN, GERMANY, ASSIGNOR T0 CHEMISCHE FABRIK GRIESHEIM ELECTRON, OF FRANKFORT-ON-THE-MAIN, GERMANY.

No yrawing.

Specification of Letters Patent. Patented Sept], 2?, 1910.

Application filed June 27, 1907. Serial No. 381,170.

1 0 all whom it may concern:

Be it known that I, KARL SoHIoK, of Griesheim-on-the-Main, Germany, have invented certain new and useful Improvements in Catalytic Bodies and Methods of Making Same, of which the following is a specification.

It has been known for a long time that platinum, when heated to 300 centigrade, causes a mixture of air and ammonia to en-' ter into reaction and form nitric oxids which form, with water at the same time produced, nitric acid and nitrous acid (see, for instance, Fehling, H andwo'rterbuch. der Ghemc'e, 1871, I, page 386, fourth paragraph). The platinum was used for these and other gaseous reactions in the form of spongy platinum, or platinum black, as it was su posed that the finer the platinum was ivided themore capable of reacting it would be and the greater would be the yield in nitric oxids, but it was found, that the yield was poor. In using other contact bodies, such for instance, as Fe O CuO, and the llke, theamount of nitrogen formed is very large, and consequently the yield in nitric oxids is correspondingly poor. Ostwald proposed to use either solid platinum, or platinum thinly/ coated with platinum black, and these at first give good yield, as much as 93 percent. of'the nitrogen in, the ammonia be ng 0x1 dized, but this favorable action soon ceases and, after a comparatively short time, the yield in nitric oxids decreases and in a few weeks, the catalytic bodies become-practlcally useless.

The present invention is based on the observation that the cause of the decrease in activity of the solid platinum and platinum coated with platinum black is due to the reaction'loosening the surface of the platinum, reducing it to a condition similar to that of spongy platinum, which, as hereinbefore stated, yields but poor quantlties of nltllc oxids. The action of platinum sponge s probably as follows: A part'of the ammonia is absorbed in the platinum sponge, or otherwise held back, and decomposed into nitrogen and hydrogen (see Fehlings H and'w-b'rterbuch der Ohemnle, I, 386, second paragraph) and .therefore escapes oxidation, while the remainder of the ammonia is oxidized to nitric oxid at the surface. Solong I as the catalytic bodies proposed by Ostwal I have, as a result of investigations and experiments, found that platinum can be satisfactorily used as the catalytic'agent, if the formation of platinum sponge be prevented, or, should it form, if its gas absorbing qualities be removed. This result I attain as follows :Platinum is, by reduction, deposited in a very thin layer of platinum black on a suitable carrier, such, for example, as quartzite, porcelain, or the like, and the contact bodies thus obtained are heated to a temperature sufficient to soften the platinum layer and cause it to unite with the body to which it is applied. The platinum black is thereby converted to microscopic small bright metallic drops and a catalytic body is obtained which is extraordinarily eiiicient and durable giving 93 to 95 per cent. yield. While the carrier bodies may be coated as described in several ways I prefer to rinse them in a solution of chlorid of platinum and after the liquid has evaporated bake the bodies thus coated withchlorid or platinum by exposure to a temperature of 1400 centigrade. The production of a uniformly .thin layer of platinum is somewhat difficult in producing large quantities of such catalytic bodies for it requires great care in order to prevent the platinum in some places forming too thick during softening, which thick layers would result in theformation of platinum sponge with the drawback aforesaid. This can be prevented by coating the'carrier with a laze which softens easily (such as feldspar and caustic potash). The further preparation of the catalytic bodies by the method hereinbefore described does not require any special care and their duration and eflicacy is. unlimited as shown by protracted'trials.

Probably the glaze is softened by the heat of I reaction during the catalytic action and penetrates into the poresof any platinum sponge that mayhap'pen to be formed, so that the said spongeloses its orosity and consequently its capacity for a sorption of ammonia.

contact body such as described.

Having thus described the invention, what is claimed is 1. The herein described method of manufacturing a platinum contact body for use in manufacturing nitric acid, consisting in coating a suitable carrier with a thin layer vof platinum and then heating the coated carrier to a temperature at which the platinum will be softened and caused to unite with the carrier, as and for the purpose described.

2. The herein described method of -manufacturing a platinum contact body for use in manufacturing nitric acid, consisting in first coating a suitable carrier with a glaze which can be readily softened, then applying to said glazed body a thin layer of platinum,

and heating the body coated as aforesaid to a temperature at which the platinum will be softened and caused to unite with the carrier, as and for the purpose set' forth.

3.'As an article of manufactureya platinum contact body for use in manufacturing nitric acid, comprising a suitable carrier coated with a readily softening glaze and having a platinum layer applied thereto in the manner described, as and for the purpose set forth.

In testimony whereof I have signed my Y name to this specification in the presence of two subscribing witnesses.

v KARL SCHICK.

Witnesses: V

FRANZ HAssLAoHER, ERWIN DIPPEL. 

